Second Battle of Ypres

The Second Battle of Ypres was fought from 22 April to 25 May 1915 on the Western Front of World War I when the Imperial German Army launched an offensive against the Entente forces at the Ypres salient in Flanders, Belgium. Ypres was the first battle in history to feature the use of chlorine gas.

Background
In the spring of 1915, the Germans were preparing a major offensive against Russia, but the development of a new weapon also tempted them to attack on the Western Front. In November 1914, the Allies had gained the Ypres salient in the First Battle of Ypres. Their line of trenches, curving to the east of the Belgian town, was overlooked by German positions on higher ground. The trenches on the left of the salient were held by French territorials and colonial troops, with the British 2nd Army, including the Canadian 1st Division, holding the front and right.

The German forces in the sector were outnumbered by the Allies, because German Chief of the General Staff Erich von Falkenhayn had transferred troops to the Eastern Front for the Gorlice-Tarnow Offensive. Falkenhayn's strategy was to stand on the defensive in the West while attacking in the East. In late 1914, Germany's scientists had begun developing the poison gas chlorine for military use. The Ypres salient was identified as a suitable location for an experimental gas attack.

Battle
The Germans surprised the Allies with their chlorine gas attack at Ypres, even though their preparations were slow and clumsy. Their plan was for gas released from pressurized cylinders to be blown across Allied lines by the wind. Some 5,700 cylinders, each weighing about 88 lb, were manhandled into position at the front and then buried under a layer of earth. The cylinders were in place by early April, but a long wait ensued because the wind was in the wrong direction. During the delay, Allied interrogation of German prisoners and a deserter produced detailed accounts of the deployment of the cylinders, but the information was not taken seriously by Allied military intelligence.

On the afternoon of 22 April, with a breeze at last blowing steadily from behind their lines, Germany's special gas troops opened the cylinders. A yellow-green cloud drifted across no man's land toward trenches held by French Zouaves from across France's North African colonies, and Algerian riflemen. Those in the frontline had little chance of escape. If they stayed in the trenches, they were killed by the chlorine in their lungs. If they climbed out, they were exposed to artillery and machine gun fire. As the gas rolled toward the rear, troops fled in panic, many choking and with eyes streaming. Meanwhile, German troops using respirators as protection advanced into a gap 4 miles wide in the Allied line. Fortunately for the Allies, their superiority in numbers prevented the Germans from fully exploiting their breakthrough. Allied reserves were brought up to block the gap and launch counterattacks. A Canadian Scottish battalion led a frontal assault on a position known as Kitchener's Wood. It succeeded in taking it, but at the expense of 75% casualties.

Fog of chlorine
Allied troops quickly found that an improvised answer to the worst effects chlorine was a wet pad placed over the mouth - at first usualoly soaked in urine, which neutralized the poison. Thus prepared, Canadian troops subjected to gassing on 24 April did not panic, and the German assault ran into fierce resistance. But the line broke where the gas attack was densest, and at the end of the day the Canadians were ordered to retreat. On 1 May, it was the turn of the British Dorset Regiment, which was attacked with chlorine at a position known as Hill 60. The men stood on the fire steps of their trenches in a fog of chlorine, shooting blindly at advancing German infantry, stopping only when disabled by poisoned lungs. By then it was clear that the Germans had increased the horror of the ewar without finding a solution to the trench stalemate.

German troops continued to have the upper hand, and gained ground piecemeal. The town of Ypres was reduced to rubble by German shelling. As the size of the salient shrank, Allied troops became dangerously crowded, making a tempting target for German artillery. Commander of the British 2nd Army, General Sir Horace Smith-Dorrien, advocated some tactical withdrawals to improve the defensive position. Annoyed by this suggestion, British commander-in-chief Field Marshal Sir John French used it as a pretext to replace Smith-Dorrien with General Herbert Plumer - who promptly made the necessary tactical withdrawals in any case. In continued fighting through May, the Germans advanced to within 2 miles of Ypres, where a new front line was stabilized on 25 May. The battle was then deemed to have ended.